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Scientists have discovered that two of the primary coral species comprising Florida's reef have become functionally extinct following a withering ocean heatwave caused catastrophic losses.

What 'Functional Extinction' Means

The almost complete collapse of these corals, which once formed the backbone of reefs in Florida and the Caribbean, indicates they are no longer able to fulfill their once vital role in constructing and maintaining reef ecosystems that support a diversity of marine life.

Ecological extinction is a stage before total extinction, a threat that now looms for many coral species.

Researchers this month alerted that a critical threshold had been reached, meaning corals around the world are likely to be wiped out due to global heating, which is raising ocean temperatures to unbearable levels.

Expert Insight

"We're running out of time," stated Ross Cunning of the new Florida study. "Extreme heatwaves are increasing in frequency and severity due to climate change, and absent immediate, ambitious actions to slow ocean warming and boost coral resilience, we face the danger of the extinction of even more corals from reefs in Florida and around the world."

The Recent Study

The new research, published in the Science journal, examined the outcome of staghorn and elkhorn corals off the Florida coast following a intense marine heatwave in 2023.

This event elevated temperatures on Florida's deteriorating coral reefs to their peak temperatures in over 150 years.

The two species are complex, reef-forming corals and are identified because they look like, respectively, the horns of stags and elks.

However, researchers who performed diver surveys of more than 52,000 colonies of the species, across 391 sites along Florida's coast, found widespread, often devastating, losses.

Geographic Effects

• Along the Florida Keys, death rates reached ninety-eight percent and even 100%, revealing a complete annihilation of the corals.
• In southeastern Florida, where temperatures have been lower, death rates were lower, at about thirty-eight percent.

Past and Current Dangers

The two Acropora species had already suffered from decades of localized impacts in Florida, such as contaminated water from pollutants that wash off the land, as well as illness.

But the 2023 marine heatwave has been lethal for these heat-sensitive species.

The 2023 event caused the ninth occurrence of bleaching on the Florida reef – a phenomenon whereby corals become heat-stressed and eject the symbiotic algae living in their tissues, causing them to become bleached white.

If temperatures stay high, the corals perish entirely.

Global Consequences

Worldwide, coral reefs are among the ecosystems most vulnerable to the human-caused climate emergency.

This presents a significant danger to:

• A quarter of all ocean life that relies upon what are effectively the marine rainforests.
• Millions of people who rely on corals to sustain fish that they can consume and earn a livelihood from.

Corals also act as a protective barrier to protect our shorelines from intense hurricanes, which are themselves being intensified by rising global temperatures.

Conservation Attempts

In a desperate attempt to prevent a decline of endangered corals, scientists have established repositories of Acropora in marine facilities and offshore coral nurseries.

Attempts have been undertaken to reseed corals on reefs in Florida, too, in an effort to restore some of the ninety percent of coral cover disappeared off the state in the last forty years.

But as climate change continues to escalate, there is slim chance of long-term survival of these species absent significant actions, scientists caution.

Further Expert Commentary

"Elkhorn species, in particular, are some of the key wave-breaking coral species in the area," said Andrew Baker, a ocean scientist at the Miami University.

"They used to be common on shallow reef tops in the Caribbean, and if we want our reefs to keep safeguarding our coastlines from inundation during storms, it is worthwhile taking extraordinary measures to ensure we don't lose these corals altogether."